This invention concerns a method and device to separate polypropylene in the processing of silk.
To be more exact, this invention concerns a method and separator device able to separate manmade fibres, and polypropylene fibres in particular, from silk schappe, that is to say, pure silk of discontinuous fibres coming from waste silk.
It is known that during recent years the old packages based on cellulose in which waste silk was conveyed from its collection points to its places of recovery and re-use have been replaced with packages containing manmade fibres and, in particular, polypropylene fibres.
The technology of the state of the art has already found a system for eliminating the cellulose fibres from the silk schappe but is powerless to do so in the case of manmade fibres.
This position entails the shortcoming that the fibres of polypropylene or other manmade materials impair the silk fibres, but the presence of these manmade fibres cannot be identified at present by any method other than dyeing.
Indeed, the only existing system to identify the polypropylene fibres is to dye the silk since the polypropylene fibres possess no affinity to dyes and remain white.
These undyed polypropylene fibres lead to an end product of an unacceptable quality, and these rejects containing polypropylene fibres cause a great increase in the production costs of the silk free of defects precisely owing to the subsequent elimination of such defects.
U.S. Pat. No. 1,565,196 discloses the purifying of silk from extraneous products such as wooden chips, leaves and straw. These products are visible and do not entail the problems of separation and purification caused by polypropylene.
In any event the method disclosed cannot be used and in fact makes the silk containing the impurities pass into an oven so that the impurities are dried, and then passes the whole mixture into a crusher, so that the impurities are removed in the form of a powder.
EP-A-0.344.729 too is not acceptable because it concerns cotton and because it proposes to remove the sugar which the insects deposit on the cotton flower and then to caramellize and pulverize the sugar.